Device for the fastening of a printing plate

ABSTRACT

In a clamping device to fasten a printing plate on the plate cylinder of a rotary printing machine, a rod is inserted between the tension bar and the printing plate end so as to be movable to produce a wedging effect. Initial tension in the plate is produced by movement of the clamping jaws which produces a uniform clamping force after which the main tension is applied by movement of the tension bar to stretch the plate.

United States Patent 1 1 3,557,695.

[72] inventor Friedrich Preuss [56] References Cited peu-lsesnburg, Germany 4 UNITED STATES PATENTS 1 pp 4751 453 862 6/1891 Hawkins 101/415.1 Flled 'July2531963 2,386,214 10 1945 Harroldetal 101/415.1

[45] Patented Jan. 26, 1971 1 1 Assignee g g t g m & 21121121 1151321 $5236.???3"""""'"::::: 13151123 f 'g z Main German 3,276,365 10/1966 Langer... 101/4151 y 3,456,587 7/1969 Hulen 101/415.1 a corporation of Germany [32] Priority July 29, 1967 Primary Examiner-William B. Penn [3 3] Germany Assistant Examiner-E. M. Coven [31] 1,611,258 Attorney-Plane & Baxley ABSTRACT: In a clamping device to fasten a printing plate on [54] DEVICE FOR THE FASTENING 0F APRINTING the plate cylinder of a rotary printing machine, a rod is in- PLATF serted between the tension bar and the printing plate end so as 12 Clams 6 Drawmg to be movable to produce a wedging effect. Initial tension in [52] US. Cl l01/415.1 the. plate is produced by'movement of the clamping jaws [51] Int. Cl B4lf 27/06 which produces a uniform clamping force after which the [50] Field of Search 101/415.1, main tension is applied by movement of the tension bar to 378, 246, 407 stretch the plate.

SHEET 2 OF 2 PATENTEDJANZSIQYI lnvemar:

DEVICE FOR THE FASTENING OF A PRINTING PLATE The invention relates to a device for fastening a printing plate on the plate or form cylinder of a rotary printing machine by means of tension bars arranged in a channel in the cylinder parallel to its axis and clamping jaws hingedly connected with the bars. The clamping jaws, which are pivotal by means of tensioning eccentrics, press the ends of the printing plate against the tension bars. The tension bars, after the clamping of the printing plate ends has taken place, are moved approximately in the peripheral direction of the cylinder for the purpose of tensioning the printing plate.

A device is already known for the fastening of printing plates (U.S. Pat. No. 3,156,184), in which the plate end is clamped between a tension bar movable approximately in the peripheral direction of the cylinder and a clamping jaw hingedly connected to the bar. The pressing force necessary for the clamping is exerted upon the plate end by pivoting the clamping jaw by means of a tensioning eccentric. However, this device has not proven itself in practice, more especially since the large pressing force necessary for clamping the plate cannot be applied solely by rotation of the tensioning eccentric, or the rotation of the tensioning eccentric cannot be carried out by a force which is acceptable with regard to easy and rapid operation of the device. More especially in the case of slightly wavy plate ends, an irregular distribution of the pressure application occurs over the width-of the plate, so that the plate ends while being tensioned are pulled out at some points and torn at other points.

In a further known plate fastening device (U.S. Pat. No. 2,386,214), the plate end is introduced into a gap of a tensioning bar movable approximately in the peripheral direction of the cylinder, and clamped fast between one gap wall and a rod held in the gap and wedgeable therein. The force wedging the rod is provided, after locking together the tensioning bar, plate end and rod, by the movement of the tensioning bar in the peripheral direction of the cylinder, that is to say as the traction exerted upon the plate for the purpose of tensioning increases, the pressure force exerted upon the plate end for the purpose of clamping also increases. This device, however, does not work satisfactorily when used with plates of different thicknesses and plates having slightly corrugated plate ends. The magnitude of the pressing force exerted upon the plate end cannot be limited and varied according to the plate thickness. Moreover, the dependency of the normal force, which is exerted upon the plate end and must reach a specific value to obtain secure clamping of the plate, upon the traction force exerted upon the plate assuming the tensile strength of the plate to be limited necessitates the use of a rod having a small wedge angle. In other words, the rod can have only a slight rise of its profile engaging the plate end in relation to the rotation of the rod. On the other hand, release of the clamping of the plate requires that the rod is rotated against a very high frictional force. Release of the clamping action is made even more difficult by the fact that the wedged rod is covered by the plate, that is, it is not readily accessible from the outside. Disengagement of a rod extending over the whole cylinder length from one side is impossible, so that the rod has been divided in the previously known device.

The present invention is directed to the problem of providing an easily and rapidly operable plate securing device, avoiding the disadvantageous properties of known devices, wherein the plate ends are held securely even when relatively high tensions are exerted upon the plates, without danger of the plate being damaged.

This problem is solved according to the invention by the arrangement of a rod known per se extending along the tension bar, between the printing plate end and the tension bar. This rod abuts against the end of the printing plate between the clamping jaw and the tension bar and is wedged between the printing plate end and the tension bar upon moving the tension bar approximately in the peripheral direction of the cylinder. Thus it is possible to exert a slight initial tension upon the printing plate end by pivoting of the clamping jaw by means of a tensioning eccentric. This initial tension can be applied rapidly and without applying a strong force and effects a very desirable smoothing of the initially possibly wavy printing plate end. It also ensures that the rod clamps the plate uniformly over its whole length, so that no localized overstressing of the plate can occur. The main tension upon the printing plate ends is subsequently applied, when the printing plate is stretched in the peripheral direction of the cylinder. Release of the clamping pressure exerted upon the plate end is again effected by means of the tensioning eccentric which is conveniently accessible and easily operated. By the combination of two elements known per se in a plate fastening device, a wedging rod can be provided with a small wedge angle thus obtaining a high clamping force, without the necessity of accepting the disadvantages thereof, because the release of the clamping force is effected at another point by means of a tensioning eccentric with a larger wedge angle. Thus for the first time by combination of the known elements a truly functional plate fastening device is produced.

According to one embodiment of the invention, the bearing surfaces of the rod, seen in the direction of movement of the tension bar, are inclined in relation to one another. On movement of the tension bar in the tensioning direction of the plate the rod is forced into a narrowing cross section and thus a clamping force is exerted upon the plate end.

In another development of the invention the rod has a noncircular cross section. The surfaces upon which the wedging rod bears can be parallel with one another in this case.

Preferably a strip is arranged between the rod and the printing plate end to be clamped, the strip surface in contact with the printing plate and being approximately parallel with the clamping surface of the clamping jaw. As a result the pressure exerted upon the plate end can be kept low, that is to say the pressing force can be distributed over a larger clamping area. At the same time a rod cross section which is suitable for the intended tilting can be selected, without danger of notching the plate. On tilting of a rod of rectangular cross section which abuts against two diagonally opposite edges, the lowest frictional forces would appear to have to be overcome.

In a further development of the invention, at the point of contact between the eccentric which pivots the clamping jaw and the tension bar and/or at the point of contact between the eccentric which pivots the clamping jaw and the clamping jaw a displaceable insert piece is interposed. In this way the friction forces which occur on the periphery of the tensioning eccentric upon rotation of the tensioning eccentric and oppose such rotation are reduced, or the friction acting upon the periphery of the tensioning eccentric can be converted from a sliding friction to a rolling friction. This assures easy actuation of the tensioning eccentric, especially in releasing the plate, even if relatively great forces act upon the tensioning eccentric after tensioning of the plate have taken place and tilting of the rod. A reduction in the friction forces is possible since no external forces, such as pull forces transmitted via the plate, have to be taken up by the tensioning eccentric in its peripheral direction. If the tensioning eccentric is mounted with sufficient play it can be disengaged with a jerk, that is to say the disengagement of the tensioning eccentric can take place by using the so-called hammer stroke effect.

Preferably a displaceable support for the eccentric is mounted on antifriction roller bodies. Thus the displacement of the support takes place with the lowest possible friction.

Preferably the rod is pressed into a nonwedging position in the absence of tensioning by the tension bar. Thus introduction and initial tensioning of the plate are precluded when the rod is already wedged. At the same time the rod and strip are secured against falling out.

The invention also provides that the surface of the clamping jaw which clamps the plate end is less rough than the opposite clamping surface engaging the plate. This ensures that sliding of the clamped-in printing plate end can take place in relation to only one of the two cooperating clamping surfaces.

It is further preferred that the opposite clamping surface has a slight rise extending along the strip. This rise is disposed opposite to a depression provided in the clamping surface of the clamping jaw and extending in the same direction as the rise. By means of a slight rise of for example 0.1 mm. the connection between plate end and strip can be significantly improved. Especially when the strip has a rough and not always uniform surface, such as is formed for example by the application of a granulated material to the surface, tension peaks as may occur at localized points can be avoided. The depression in the clamping surface of the clamping jaw lying opposite to the rise prevents this rise from influencing the conditions prevailing between clamping jaw surface and plate end.

Several embodiments of the invention are illustrated in the accompanying drawings, wherein:

FIG. 1 shows a partial cross section through a form or plate cylinder along the line I-l in FIG. 4;

FIG. 2 shows a partial cross section, supplementing the par tial cross section in FIG. 1, through a form cylinder, the section having been effected however at a different point over the length of the form cylinder, namely in accordance with the line II-II in FIG. 4;

FIG. 3 shows a part of a lateral elevation of a plate fastening device and of a longitudinal section through a form cylinder;

FIG. 4 shows a plan view of FIG. 3;

FIG. 5 shows a partial cross section of a plate fastening device in a modified form of the invention and on a larger scale; and

FIG. 6 shows a detail of FIG. 1 showing the plate end to be clamped, on an enlarged scale.

Fastening devices 5 and 6 for the front end 3 and the rear end 4 respectively of a printing plate are arranged in a channel 1 in a form cylinder 2. The two devices are completely similar so that the same reference numerals have been used for the same parts. A tension bar 7 is slidingly mounted on a slide rail 8 (see also FIG. 3) extending approximately in the peripheral direction of the cylinder and firmly connected with the cylinder body. The rail engages a groove 9 provided in the tension bar 7. The tension bar 7 is pressed in one direction (upwards in FIG. 4) by a spring 11 bearing on a protuberance secured to the cylinder body, and abuts via the end 12 of a screw 13, protruding from the tension bar 7 against a wall of the cylinder channel 1. The screw 13 is threaded into a threaded bore 15 in the tension bar 7 so that by rotation of the screw 13 in clockwise direction the tension bar 7 is moved in the tensioning direction of the plate, that is to say to the right in FIG. 1, while on rotation of the screw 13 in counterclockwise direction the spring 11 moves the tension bar 7 in the opposite direction. The screw 13 can be locked in relation to the tension bar 7 by means of a nut 14. The position of the tension bar 7 in its longitudinal direction (to the right or left in FIG. 3) is controlled by two screws 16 which determine the distance from the cylinder body (only one screw is shown, since only one tension bar end is illustrated in FIG. 3); the said distance can be modified by appropriate inward or outward rotation of the screws 16. A clamping jaw 17 is pivotal about the center point 18 of a semipherically formed head 19 of a screw 20 screwed into the tension bar 7. The pivotal axis of the clamping jaw 17, which passes through the point 118, can be shifted by screwing screw 20 into or out of the tension bar 7, so that the distance between the clamping jaw 17 and the tension bar 7 can be varied thereby compensating for different thicknesses of the printing plates. A plurality of such screws 20 is provided. One or more compression springs 21, guided in a blind bore 22 provided in the tension bar 7 bias the clamping jaw 17 into its pivotal position ready for insertion of the plate ends 3, 4. A rod 23 of rectangular cross section rests with one of its corners in a groove 24 of triangular cross section in the tension bar 7 (see also FIG. 6), the apex angle of the groove is being somewhat larger than a right angle. The opposite comer of the rod which extends into a further groove 25 of triangular cross section provided in a bar 26; groove 24 also has an obtuse apex angle. The bar 26 is biased toward to the right (see FIG. I) by a leaf spring 27 screwed fast to the tension bar 7, so that the surfaces of the grooves 24, 25 bear on the corresponding surfaces of the rod 23. The plate end 3 or 4 is fitted between a roughened surface 28 of the bar 26 and the clamping surface 29 of the clamping jaw 17. Upon relative movement of bar 26 and tension bar 7 the plate end is clamped tight due to the fact that the rod 23 tips about is corner in the groove 24 and the edge of the rod 23 lying diagonally opposite to the pivot point describes an arc. Prior to this clamping operation the distance of the bar 26 from the clamping surface 29 of the clamping jaw 17 is adjusted according to the thickness of the printing plate by rotation of the screws 20. By rotation of a tensioning eccentric 30, the wedge angle of which is greater than that of the rod 23, an initial tension is exerted upon the printing plate end 3 or 4. The tensioning eccentric 30 is formed as an eccentric shaft which is loosely mounted in brackets 31 (only one bracket is shown) secured on the ends of the tensioning bar 7. Eccentric 30 abuts against a protuberance 32 of the clamping jaw 17 and against the tensioning bar 7. Shims 33 are interposed between clamping jaw and the tensioning eccentric and further shims 35 resting on needles 34 are interposed between the tensioning eccentric 30 and the tension bar 7. The tensioning eccentric 30 is further supported over its length by walls 36 screwed to the tension bar 7. For the purpose of rotation of the tensioning eccentric 30 its ends are formed as hexagons 37 in which bores 38 are provided for the engagement of a tool. A pin 39 protruding radially from the shaft limits the angle of rotation of the tensioning eccentric 30, in that it abuts against stop surfaces 40, 41 provided on the mounting brackets 31. The roughened surface 28 of the strip 26 (see FIG. 6) includes a ridge 128 extending along the strip 26, while a depression 129 of equal length is machined into the clamping surface 29 of the clamping jaw 17.

FIG. 5 shows a fastening device similar in structure and function to the previously described one except that rod 23 is replaced by a rod 23a. As is evident from the figure, the crosssectional outline of rod 23a is such that it perfonns the function of bar 26 also which thus can be eliminated. It coacts with the jaw 17 with a curved roughened surface.

I claim:

l. A device for releasably fastening a printing plate to a form cylinder having an axial channel in its peripheral wall, said device comprising in combination:

a tension bar lengthwise disposed in said channel;

a means for displacing said bar parallel to its axis in either circumferential direction to efiect tensioning and releasing, respectively, of the printing plate to be fastened;

a two-arm clamping jaw pivotally supported by one portion of said bar, said jaw being pivotal into and out of a position clamping the end of said plate between the jaw and the tension bar;

an eccentric means rotatably disposed between one arm of the jaw and the tension bar and supported by the latter, rotation of said eccentric means pivoting the clamping jaw into and out of its clamping position;

a wedge means interposed between the other arm of the clamping jaw and the tension bar, said wedge means being supported by another portion of said tension bar and tiltable into and out of a wedging position by displacement of said bar in either circumferential direction; and

placement of a printing plate end between said other arm of the clamping jaw and the wedge means and movement of the jaw into the clamping position by rotation of the eccentric means applying an initial clamping force to said plate end and subsequent displacement of the tension bar in the tensioning direction causing tilting of the wedge means into the wedging position thereby applying a final clamping force to the plate end, release of the plate end being effected by rotating the eccentric means in opposite direction and displacing the tension bar in the releasing direction.

2. The fastening device according to claim 1 wherein spring means bias said wedge means out of the wedging position.

3. The fastening device according to claim 1 wherein said wedge means has a smaller effective angle of attack than the eccentric means.

4. The fastening device according to claim 1 wherein said eccentric means and said wedge means extend substantially across the length of the tension bar.

5. The fastening means according to claim 1 wherein said eccentric means comprises a cylindrical roller rotatable about an eccentric axis and said wedge means comprises a rod ex tending parallel to said roller and having a noncircular cross section, the wedging position of said rod being the angular position thereof in which the rod acts with its maximal width upon said other arm of the clamping jaw thereby wedging the interposed plate end against the respective arm of the clamping jaw.

6. The fastening device according to claim 5 wherein the portion of the wedging rod supported by the tension bar has a substantially triangular cross section, said tension bar including a lengthwise elongate groove of substantially triangular cross section receiving therein the wedging rod, the apex angle of said groove being larger than the apex angle of the wedging rod to permit limited tiling of the rod in the groove.

7. The fastening device according to claim l-wli erein a pressure bar is interposed between said other arm of the clamping jaw and said wedge means, said wedge means acting upon one side of the pressure bar, the opposite side of the pressure bar coacting with said other arm of the jaw for clamping the printing plate end between said bar and said other arm.

8. The fastening device according to claim 7 wherein the surface of said opposite side of the pressure bar has a rougher surface configuration than the facing surface of said other arm of the clamping jaw.

9. The fastening device according to claim 7 wherein the facing surfaces of the pressure bar and the respective clamping jaw arm are substantially flat mutually parallel surfaces.

10. The fastening device according to claim 7 wherein the facing surfaces of the pressure bar and the respective clamping jaw arm have a lengthwise elongate rib and groove respectively in engagement with each other.

11. The fastening device according to claim 1 wherein a generally plate-shaped support member is interposed between the eccentric means and the tension bar, said support member being slidable on the tension bar.

12. The fastening device according to claim 11 wherein antifriction rollers support said support member on the tension bar. 

1. A device for releasably fastening a printing plate to a form cylinder having an axial channel in its peripheral wall, said device comprising in combination: a tension bar lengthwise disposed in said channel; a means for displacing said bar parallel to its axis in either circumferential direction to effect tensioning and releasing, respectively, of the printing plate to be fastened; a two-arm clamping jaw pivotally supported by one portion of said bar, said jaw being pivotal into and out of a position clamping the end of said plate between the jaw and the tension bar; an eccentric means rotatably disposed between one arm of the jaw and the tension bar and supported by the latter, rotation of said eccentric means pivoting the clamping jaw into and out of its clamping position; a wedge means interposed between the other arm of the clamping jaw and the tension bar, said wedge means being supported by another portion of said tension bar and tiltable into and out of a wedging position by displacement of said bar in either circumferential direction; and placement of a printing plate end between said other arm of the clamping jaw and the wedge means and movement of the jaw into the clamping position by rotation of the eccentric means applying an initial clamping force to said plate end and subsequent displacement of the tension bar in the tensioning direction causing tilting of the wedge means into the wedging position thereby applying a final clamping force to the plate end, release of the plate end being effected by rotating the eccentric means in opposite direction and displacing the tension bar in the releasing direction.
 2. The fastening device according to claim 1 wherein spring means bias said wedge means out of the wedging position.
 3. The fastening device according to claim 1 wherein said wedge means has a smaller effective angle of attack than the eccentric means.
 4. The fastening device according to claim 1 wherein said eccentric means and said wedge means extend substantially across the length of the tension bar.
 5. The fastening means according to claim 1 wherein said eccentric means comprises a cylindrical roller rotatable about an eccentric axis and said wedge means comprises a rod extending parallel to said roller and having a noncircular cross section, the wedging position of said rod being the angular position thereof in which the rod acts with its maximal width upon said other arm of the clamping jaw thereby wedging the interposed plate end against the respective arm of the clamping jaw.
 6. The fastening device according to claim 5 wherein the portion of the wedging rod supported by the tension bar has a substantially triangular cross section, said tension bar including a lengthwise elongate groove of substantially triangular cross section receiving therein the wedging rod, the apex angle of said groove being larger than the apex angle of the wedging rod to permit limited tiling of the rod in the groove.
 7. The fastening device according to claim 1 wherein a pressure bar is interposed between said other arm of the clamping jaw and said wedge means, said wedge means acting upon one side of the pressure bar, the opposite side of the pressure bar coacting with said other arm of the jaw for clamping the printing plate end between said bar and said other arm.
 8. The fastening device according to claim 7 wherein the surface of said opposite Side of the pressure bar has a rougher surface configuration than the facing surface of said other arm of the clamping jaw.
 9. The fastening device according to claim 7 wherein the facing surfaces of the pressure bar and the respective clamping jaw arm are substantially flat mutually parallel surfaces.
 10. The fastening device according to claim 7 wherein the facing surfaces of the pressure bar and the respective clamping jaw arm have a lengthwise elongate rib and groove respectively in engagement with each other.
 11. The fastening device according to claim 1 wherein a generally plate-shaped support member is interposed between the eccentric means and the tension bar, said support member being slidable on the tension bar.
 12. The fastening device according to claim 11 wherein antifriction rollers support said support member on the tension bar. 